Rub the wild boar all over with 2 tablespoons of the softened duck fat. Season with salt and pepper. In a small bowl, mix paprika, garlic powder, and dry mustard. Rub mixture evenly over roast. In a large skillet, heat the remaining 2 tablespoons of duck fat over high heat. Brown all sides of each piece of wild boar.
In a mixing bowl, combine 6 cloves minced garlic, green onions, salt, pepper and granulated garlic. Make incisions at equal space around the top of roast and stuff with garlic mixture. Season outside of roast well with salt, pepper and granulated garlic. In a roasting pan, heat olive oil over medium-high heat then brown boar on all sides.
Brown all sides of each piece of wild boar. Add onion, carrots, parsley, and garlic to your slow-cooker. Place the wild boar pieces on top of the vegetables. Add tomatoes, brown sugar, Armagnac (if using), and demi-glace. Cover and cook on low for 8 hours, turning wild boar once halfway through cooking.
Any leftovers can be shredded for BBQ boar sandwiches, tacos, or even nachos. Remove the netting from the wild boar and discard. Pat the roast dry with paper towels then cut into two pieces. Rub the wild boar all over with 2 tablespoons of the softened duck fat. Season with salt and pepper.